1. Field of the Invention
The present invention relates to a compound useful for manufacturing salacinol and a method for manufacturing the compound. The present invention also relates to a method for manufacturing salacinol, methods for protecting and deprotecting a diol group, and a protective agent for a diol group.
2. Description of the Related Art
In traditional Indian medicine, Salacia reticulata which is a climbing tree of the genus Salacia is used for treating diabetes. Salacinol is a component contained in plants of the genus Salacia such as Salacia reticulata and has a strong α-glucosidase inhibitory activity (Tetrahedron Letters, Vol. 38, No. 48, pp. 8367-8370 (1997)). Salacinol is obtained from, for example, extracts of plants of the genus Salacia (JP3030008B). However, the supply of plants of the genus Salacia is small, and it is difficult to easily obtain the plants. Therefore, methods for manufacturing salacinol and analogs thereof by synthesis are being investigated in various ways (JP5053494B, JP4939934B, and JP2002-179673A).
JP5053494B describes a manufacturing method in which a cyclic sulfuric acid ester protected with a benzylidene group is reacted with a thioarabinitol derivative protected with a benzyl group.
JP4939934B describes a manufacturing method in which a cyclic sulfuric acid ester protected with a benzylidene group is reacted with a thioarabinitol derivative protected with a benzyl group.
JP2002-179673A describes a manufacturing method in which a cyclic sulfuric acid ester protected with an isopropylidene group is reacted with thio-D-arabinitol.
In a case where organic synthesis is performed using a compound having a functional group such as an amino group, a hydroxy group, or a carboxy group, in order to prevent the functional group from affecting the reaction, generally, the functional group is protected. Furthermore, in a case where the number of functional groups is 2 or greater, in order to selectively cause only an intended functional group to react, other functional groups are protected.
A protective group not only needs to stably protect a target functional group but also needs to be easily removed if necessary. Therefore, in organic synthesis, it is important to deprotect only a protective group bonded to a specific functional group under appropriate conditions.
For example, as protective groups for an amino group, a hydroxy group, or a carboxy group, various protective groups have been developed (Protective Groups in Organic Synthesis, 4th edition, John Wiley & Sons, INC (2007)). Furthermore, as protective groups for a 1,2-diol group or a 1,3-diol group (hereinafter, referred to as a “diol group” in some cases), a cyclic acetal, a cyclic ketal, a cyclic orthoester, and the like are known.
As a protective group for a diol group, an alkoxycarbonylethylidene group is known (Organic Letters, Vol. 2, No. 18, pp. 2809-2811 (2000)).
Meanwhile, a method for manufacturing diethyl 2-(5-pentyl-1,3-dioxan-2-yl)malonate by reacting 2-(hydroxymethyl)heptanol with diethyl ethoxymethylene malonate in the presence of p-toluenesulfonic acid is known (DE19525314B).